1. Field of the Invention
The present invention relates to an image forming apparatus that forms a crease in a recording medium and forms an image.
2. Description of the Related Art
When a folding process is performed on paper after an image is formed by an image forming apparatus, as illustrated in FIGS. 1A and 1B, an image formed in a mountain portion Pa or a valley portion Pb of a crease of paper P may be peeled off (that is, an image may crack). The folding process is a process of folding the paper in two. A crease forming device that forms a crease in a portion of paper to be folded before performing the folding process has been proposed (see Japanese Patent Application Laid-open No. 2008-81258). In the crease forming device, a crease blade abuts on the paper to form a crease in an abutting portion. A crease forming process is referred to as a crease process, and the crease forming device is called a creaser.
In the crease forming device disclosed in Japanese Patent Application Laid-open No. 2008-81258, transportation of paper needs to be stopped when forming the crease in the paper. In addition, with regard to the crease forming device disclosed in Japanese Patent Application Laid-open No. 2008-81258, the crease forming process needs to be performed on every sheet of paper that is to be subjected to the folding process, so that there is a problem in that productivity of the crease forming process is low. Furthermore, since the crease blade abuts on every sheet of paper that is to be subjected to the folding process, the crease blade is easily worn out due to the repulsive force from a cradle for a crease blade, whereby the replacement cost of the crease blade increases. Still further, when the crease forming device is broken due to some reasons while the paper is transportable, the crease forming process may not be performed and as a result thereof there may be a time period in which the process can not be performed at all (hereinafter, referred to as “downtime”).